Separable drill bit



Aug. 25, 1936.

J. B. BAKER 2,052,011 SEPARABLE DRILL BIT Filed Aug. 6, 1934 I a) w YEA/roe; fim M,

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Patented Aug. 25, @936 UNITED STATES PATENT OFFICE John-B. Baker, Canton, Ohio, asslgnor to The Timken Roller Bearing Company, Canton, Ohio, a corporation of Ohio Application August 6, 1934, Serial No. 738,591

' 4 Claims. (01. 255-64) 583,256 filed December 26, 1931.

The invention consists principally in a separable drill bit construction whose threads have a substantially sinuous contour but in which the sides of the threads are provided with flattened bands. The invention further consists in the separable drill bit and in the parts and combinations and arrangements of parts hereinafter described and claimed.

In the accompanying drawing, which forms part of this specification and wherein like symbols refer to like parts wherever they occur,

Fig. l is an elevation of a drill rod and separable drill bit provided with threaded portions embodying my invention, the bit being. shown in section,

Fig. 2 is an enlarged diagrammatic view showing the thread contour,

Fig. 3 is an enlarged diagrammatic view showing the thread contour of the application of which the present application is a division and indicating the development of the present thread therefrom; and

Fig. dis a sectional view similar to Fig. 1, showing a construction wherein the bit has a sleeve portion abutting against a shoulder on the drill rod.

Great difliculty has been found in making threaded bits which will not bind upon the threaded end of the drill rod. Various thread structures have been devised, such as a thread having a substantially continuous curved contour. In all previous constructions, however, repeated impact tends to flatten out portions of the sides of the threads and pack the metal into the spaces at the crest and hollows of the threads, thereby causing the parts to become tightly jammed together and frequently causing the parts to break. According to my invention, the tendency for portions of the threads to become flattened is obviated and the parts continue to be separable under the most severe usage.

The drawing illustrates the usual hexagonal drill rod l having a threaded end A cooperating with the threads B of an interiorly threaded bit member 21. erally curving contour. One thread, illustrated as being the thread A of the drill rod, has a curved crest 3 whose radius of curvature R is relatively long.

The threads A and B have-a gen- The'other thread B has its trough portion curved to conform to the curvature of said crest 3. Both threads A and B have flattened bands 6 along their sides that merge into the curved portions of the threads.

The trough of said thread A has a flat bottom 4' extending parallel to the bit axis and connecting the lower edges of opposing flat bands 6'. The crest 5 of-the other thread B is correspondingly flattened. The degree of curvature of the curved crest 3 and the mating trough, the height of the flattened zones 6' and the width of the flat bottom 4 of the trough may be varied to suit conditions. The preferred proportions are indicated in Fig. 3, 15

,which is' a diagrammatic sketch' of the thread contour of said parent application Serial No. 583,256, of which the thread of the present application is a modification. As shown in Fig. 3, the radius of curvature R. of the crest 3 of the 20 thread A is greater than the radius of curvature R of the base portion. Thus, the crest 3 of the thread A of the drill rod is wide and flat as compared with the trough 4 between the base portions of the thread A. The crest 5 of the other thread 25 B has a shorter radius of curvature r than that r of the base portion of the thread B. As is indicated by dotted lines, the present thread may be described as characterized by the filling up of the lower portion of the trough of the thread A up 30 to the level of the lower margins of the flattened bands 6' and the corresponding flattening of the crest 5' of the otherthread.

In the. construction shown in Fig. 4, the flat end face 17 of the sleeve portion of the bit abuts 35 against an annular shoulder 8 on the end of the drill rod. By this arrangement, the drilling force is transmitted to the bit through the sleeve and hence to the wing portions 9 of the cutting teeth it. This arrangement is particularly adapted for cooperation with the hereinbefore described thread contour.

The above described threaded construction does not bind or jam under the most severe usage. The threads are not battered out of shape. The

, construction is obviously adapted for variation to meet different conditions by changing the relative dimensions of the thread crests and thread troughs.

What I claim is:

1. A separable drill bit construction comprising a threaded drill rod and an interiorly threaded bit thereon, s'aid threads having flattened zones along their sides disposed obliquely with respect to the axis of the bit, the thread of said drill rod 55 having a convexly curved crest portion merging into said flattened zones and having a trough portion with a flat bottom extending parallel to the bit axis at the level of the lower portions 0! said flattened zones and the thread of said bit being shaped to conform to said flrst thread, havand having a trough portion with a flat bottom extending parallel to the bit axis at the level of the lower portions of said flattened zones and the bit thread being shaped to conform to said drill rod thread, having a concave trough portion and a flat crest portion.

3. A separable drill bit construction comprising a threaded drill rod and an interiorly threaded bit thereon, said threads having flattened zones along their sides, the thread of said drill rod having a convexly curved crest portion merging into said flattened zones and having a trough portion with a flat bottom extending parallel to the bit axis at the level of the lower portions 01' said flattened zones and the thread of said bit being shaped to conform to said flrst thread, having a concave trough portion and a flat crest portion.

4. A separable drill bit construction comprising a threaded drill rod and an interiorly threaded bit thereon, said threads having flattened zones along their sides, the thread of said drill rod having a convexly curved crest portion merging into said flattened zones and having a trough portion with a flat bottom extending parallel to the bit axis at the level of the lower portions of said flattened zones and the thread of said bit being shaped to conform to said flrst thread, having a concave trough portion and a flat crest portion,

said drill rod having a shoulder and said bit hav- 20 JOHN B. BAKER. 

